1. Field of the Invention
The present invention relates to an elevator vibration reducing device which actively reduces horizontal vibrations of a car in an elevator system.
2. Description of the Related Art
As a result of the recent increase in building height, high-speed/high-lift elevators have been developed. In such high-speed/high-lift elevators, an improvement in terms of riding comfort is among the technical concerns involved. In particular, one of the important issues is how to mitigate rolling (horizontal vibrations) of the car. Rolling of the car is attributable to an insufficient degree of straightness of the guide rails, rolling of the wire rope, fluctuations in wind pressure during the traveling of the car, etc. All of those factors become more serious as the speed and lift of the elevator become higher.
To cope with this, up to now, there has been proposed a so-called active type vibration reducing device (roller guide device), which detects the horizontal acceleration of the car and applies a force to a guide roller so as to cancel this acceleration to thereby reduce the horizontal vibrations. This active type vibration reducing device, however, has a rather complicated control device including a controller, power amplifier, etc, which may lead to an occurrence of a trouble such as failure and malfunction.
For example, JP 08-333068 A discloses a device in which the output of a detecting device and a set value are compared with each other in each operation mode to thereby detect any failure. Further, JP10-279214 A discloses a device which makes a judgment as to whether the gap between an actuator coil and a reaction bar is within a permissible range or not. The former device makes a judgment as to whether active control is being executed or not, whereas the latter device makes a judgment as to whether the result of active control is within a permissible range or not.
The above-mentioned conventional active type vibration reducing devices have a problem in that, for example, when the passenger jumps about in the car, the resultant vibration of the car may cause generation of a transient signal in the active type vibration reducing device, thereby damaging the active type vibration reducing device. Further, if the device should be out of order, the passenger would suffer loss of riding comfort.